The Distribution of Growth and Cell Division in the Fruit of Cox's Orange Pippin

An apple fruit may be treated as approximately spherical, butallometric analysis shows that its growth is far from uniformlydistributed throughout its tissues. Along the fruit axis, longitudinal(i.e. lengthwise) growth is most rapid at the eye end and slowestat the stalk end, and in each region is slower than transversegrowth in the equatorial zone (i.e. growth in diameter). Onthe surface of the fruit cheek longitudinal growth is most rapidin the equatorial region and slower at the stalk and eye ends;growth at the eye end is slightly slower than at the stalk end.Near the equator, longitudinal growth of the cheek is also fasterthan latitudinal growth, despite the slower growth in over-allfruit length. In the transverse plane at the equator, growthis initially much faster in the cortex (the outer tissues) thanin the pith (the inner tissues). Later, about one month afterblossom, there is practically no difference in the growth-ratesof the cortex and pith. The change in the relative transverse growth-rates of the cortexand pith occurs at about the same time as cell division in thecortex stops, and at this time also there is an increase inthe rate of expansion of the air-spaces, relative to growthin fruit diameter. Other aspects of growth, such as growth inover-all length or weight, both relative to fruit diameter,do not appear to change in any way when cell division stops. Cell division in the epidermis continues for a longer time thanin the cortex, and accounts for a greater proportion of tissuegrowth. Allometric analysis of growth in cell size shows thatcell division in the epidermis stops when the fruit is about45 mm in diameter, or about 65–70 days after blossom.The same data show that in the stalk and eye cavities, longitudinalgrowth of the cheek is substantially faster than latitudinalgrowth.